The present invention relates to modified diene polymer rubbers having an improved impact resilience and a low hardness at low temperatures, and more particularly to a process for preparing modified elastomeric polymers of conjugated diene compounds by introducing particular atomic groups to conjugated diene polymers, and a rubber composition containing the same.
Conjugated diene polymers, such as polybutadiene and a styrene-butadiene copolymer, have hitherto been used as rubbers for automobile tire treads. In recent years, from the viewpoint of demands in low fuel cost for automobiles and in running safely on snow and ice roads, rubber materials having a low rolling resistance and a large gripping force on ice and snow roads have been desired as rubbers for automobile tire treads.
The rolling resistance is correlative to the impact resilience of polymers. The rolling resistance decreases with increasing impact resilience. On the other hand, it is known that the grip force on snow and ice roads is correlative to the hardness at low temperatures, and that the smaller the hardness at low temperatures, the larger the grip force on snow and ice roads. Known rubber materials are not satisfactory in these properties for practical use.
It is an object of the present invention to provide a conjugated diene rubber having an improved impact resilience and a low hardness at low temperatures.
A further object of the present invention is to provide a process for modifying a conjugated diene polymer to improve its impact resilience and to lower its hardness at low temperatures.
A still further object of the present invention is to provide a conjugated diene rubber composition capable of providing a cured product improved in impact resilience and in hardness at low temperatures.
These and other objects of the present invention will become apparent from the description hereinafter.